The present invention is related to screw drivers and more particularly to a hand-operated screw driver with high driving speed/high torque force alternative selection mechanism, which can be conveniently alternatively changed to reduce the torque force and increase the speed or reduce the speed and increase the torque force in driving a screw driver blade to turn a screw according to requirement.
Screw driver is a tool used for turning screws, having a blade that fits into the slot in the head of the screw. While driving a screw of 20 screw thread pitches by a hand-operated screw driver of the prior art, a screw must be turned 20 runs to completely fasten in an object. In actual practice to drive a screw into an object, more torque force is required only when a screw is approximately driven inside an object to the limit. When less torque force is required, same consumption of time may be required when a hand-operated screw driver is used. When less torque force is required, one may wish to drive a screw faster. However, this can not be achieved by using a hand-operated screw driver of the prior art.